Enantioselective component selection in multicomponent supramolecular gels

We investigate a two-component acid-amine gelation system in which chirality plays a vital role. A carboxylic acid based on a second generation l-lysine dendron interacts with chiral amines and subsequently assembles into supramolecular gel fibers. The chirality of the amine controls the assembly of the resulting diastereomeric complexes, even if this chirality is relatively "poor quality". Importantly, the selective incorporation of one enantiomer of an amine over the other into the gel network has been demonstrated, with the R amine that forms complexes which assemble into the most stable gel being primarily selected for incorporation. Thermodynamic control has been proven by forming a gel exclusively with an S amine, allowing the R enantiomer to diffuse through the gel network, and displacing it from the "solidlike" fibers, demonstrating that these gels adapt and evolve in response to chemical stimuli to which they are exposed. Excess amine, which remains unincorporated within the solidlike gel fiber network, can diffuse out and be reacted with an isocyanate, allowing us to quantify the enantioselectivity of component selection but also demonstrating how gels can act as selective reservoirs of potential reagents, releasing them on demand to undergo further reactions; hence, component-selective gel assembly can be coupled with controlled reactivity

Synthesis of constrained alpha-amino acid derivatives via ring-closing olefin metathesis

Five and seven membered constrained alpha-amino acid derivatives were synthesized using ring-closing metathesis reaction as a key step. (C) 1998 .

A new synthetic approach to 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid (Tic) derivatives via enyne metathesis and the Diels-Alder reaction

Various subtituted 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid (Tic) derivatives are synthesized via enyne metathesis and the Diels-Alder reaction

Synthesis of dibenzocyclobutenylglycine derivatives

Several dibenzocyclobutenylglycine derivatives 9-12 have been prepared by dialkylation of ethyl isocyanoacetate 8 under NaH/DMSO reaction conditions

Allylation of caged diketones via fragmentation methodology

Fragmentation methodology was utilized to allylate some polycyclic diketones where ionic reactions are inappropriate. These allylated derivatives serve as useful precursors for the synthesis of higher polyquinanes

Synthesis of useful benzocyclobutene building blocks via the Suzuki-Miyaura coupling reaction

A general and simple methodology for 3,6-diaryl benzocyclobutene (BCB) derivatives is reported using the Suzuki-Miyaura coupling reaction as a key step. Some of these building blocks are useful for the synthesis of a variety of BCB-based polymers

Synthesis of constrained alpha-amino acid derivatives via enyne metathesis reaction

Synthesis of a diene building block via enyne metathesis reaction and its usage in the preparation of constrained alpha-amino acid derivatives is described. (C) 1998 .

Synthesis of constrained alpha-amino acid derivatives via Diels-Alder approach

Synthesis of new five and seven membered outer ring diene building blocks containing alpha-amino acid moiety and their usage in the preparation of the constrained amino acid derivatives is described. (C) 1998 .

Constrained phenylalanine derivatives by enyne metathesis and Diels-Alder reaction

A conceptually new approach for the synthesis of indane-based alpha -amino acid derivatives is reported. In this regard, the synthesis of five-membered exocyclic and five-membered inner-outer ring diene building blocks (7 and 15) containing alpha -amino acid moieties is described. Diene 15 is prepared by an enyne metathesis reaction as a key step. In this paper, a full account of our work regarding the Diels-Alder reaction of these dienes with various dienophiles, and the subsequent oxidation of the cycloadducts to give various indane-based alpha -amino acid derivatives is reported

Design and synthesis of polycyclic indoles under green conditions via Fischer indolization

A simple and useful synthetic route to aza-polyquinane derivatives involving Fischer indolization under green conditions has been demonstrated. Selenium dioxide is found to be useful for oxidizing some of these indole derivatives